U2 Lecture 6

Question 1

What factors affect bone density?

Answer 1

Diet, hormones and exercise

Question 2

What are the dietary categories that affect bone density?

Answer 2

Minerals and Vitamins

Question 3

What minerals affect bone density?

Answer 3

Calcium and phosphorus (also magnesium, fluoride, and manganese)

Question 4

What vitamins affect bone density?

Answer 4

Vitamin A, C, D, K B12

Question 5

What does vitamin A do?

Answer 5

Stimulates activity of osetoblasts

Question 6

What does vitamin C do?

Answer 6

Needed for collagen synthesis

Question 7

What does vitamin D do?

Answer 7

Stimulates calcium absorption

Question 8

What does vitamin K, B12 do?

Answer 8

Needed for synthesis of bone proteins

Question 9

Define calcium homeostasis

Answer 9

Maintaining adequate calcium levels in the body

Normal Range: 8.5 - 11 mg/dL

Question 10

Why is calcium homeostasis important?

Answer 10

Membrane excitability, blood clotting and intracellular activity (second messenger

Question 11

How does the body control calcium entry and exit from blood?

Answer 11

Through level of storage in bone, through level of kidney excretion, and through intestinal absorption levels

Question 12

Extracellular fluid Ca2+ represents how much of total body calcium?

Answer 12

1% but it is highly regulated

Question 13

What hormones are involved in calcium homeostasis?

Answer 13

Calcitonin, Parathyroid hormone, and calcitriol (Vitamin D)

Question 14

What type of molecule is Calcitonin?

Answer 14

Polar with H bonding

Question 15

Calcitonin stimulus

Answer 15

High blood calcium

Question 16

Calcitonin source

Answer 16

Thyroid gland (parafollicular cells “C cells”)

Question 17

Calcitonin target tissues

Answer 17

Bone, kidney, and intestine

Question 18

Calcitonin actions

Answer 18

Goal: DECREASE blood Ca2+ concentration

• inhibits osetoclast activity (decreased bone resorption)
• increases excretion of calcium at kidney
• inhibits intestinal absorption of calcium

Question 19

Calcitonin end result

Answer 19

DECREASE in blood calcium concentration

Question 20

What type of molecule is the parathyroid hormone?

Answer 20

Polar

Question 21

Parathyroid hormone stimulus

Answer 21

Low blood calcium

Question 22

Parathyroid hormone source

Answer 22

Parathyroid gland

Question 23

Parathyroid hormone target tissues

Answer 23

Bone, kidney, intestine

Question 24

Parathyroid hormone actions

Answer 24

Goal: INCREASE blood Ca2+ concentration

• stimulates osteoclast activity (increased bone resorption)
• Decreases excretion of calcium at kidney
• stimulates intestinal absorption of calcium and promotes calcitriol (active vit. D) action

Question 25

Parathyroid hormone end result

Answer 25

INCREASE blood calcium concentration

Question 26

Define negative feedback

Answer 26

When levels inside the body get too extreme, the body counter acts them and does the opposite

Question 27

Negative feedback regulation of blood Ca2+ concentration

Answer 27

When blood calcium levels get too high, calcitonin is released When blood calcium levels get too low, Parathyroid hormone is released

Question 28

What type of molecule is Calcitriol

Answer 28

Calcitriol is active vitamin D - Very non-polar - hydrophobic - fat soluble - steroid hormone- derived from cholesterol (lipophillic / hydrophobic)

Question 29

Vitamin D pathway

Answer 29

- Starts in 2 places: skin or intestine - Skin - light hits vit. D in skin then turns it into vit. D3. Then goes through blood to liver - Intestine - get dietary vit. D3 from fish oil, egg yolk, milk and goes straight to liver through blood - In liver, all vit. D3 turns into 25-hydroxycholecalciferol - goes through blood again to kidney where the active form of vit. D is (calcitriol), PTH will increase levels of Ca2+ if there's low blood calcium

Question 30

Calcitriol stimulates

Answer 30

It stimulates osetoclast activity (bone resorption)

Question 31

Calcitriol actions

Answer 31

- Decreases calcium excretion at the kidney | - Increases calcium absorption at the intestine (works well with PTH to stimulate absorption)

Question 32

Calcitriol end result

Answer 32

INCREASE blood calcium

Question 33

What is the recommended Ca2+ intake for young adults?

Answer 33

1000 mg to avoid bone loss

Question 34

What hormones act on osteoclasts?

Answer 34

Calcitonin and parathyroid hormone

Question 35

What hormones act on osteoblasts?

Answer 35

growth hormone (sometotropin) and estrogen/ testosterone

Question 36

Growth Hormone (GH or Somatotropin)

Answer 36

- stimulates cell growth and protein synthesis (collagen) - stimulates formation of insulin like growth factors (IGF's) -> stimulates osteoblast activity -> stimulates bone formation

Question 37

Skeletal disorders associated with GH

Answer 37

Pituitary dwarfism, pituitary gigantism, acromegaly

Question 38

Pituitary dwarfism

Answer 38

decrease in GH, slow epiphyseal growth

Question 39

Pituitary gigantism

Answer 39

increase in GH, high epiphyseal growth

Question 40

Acromegaly

Answer 40

Increase in GH after puberty, thickening of bone

Question 41

Estrogen and Testosterone

Answer 41

- Both stimulate osteoblast activity -> stimulate bone formation - Levels increase at puberty: bone growth/ spurts, eventually cause closure of epiphyseal plates bc osteoblast/osteoclast activity is greater than chondrocyte activity - levels decrease with old age